.form-container {
  width: 50vh;
  display: flex;
  justify-content: center;
  flex-direction: column;
  align-items: center;
  min-height: 20em;
  background: rgba(18, 18, 18);
  border-radius: 3px;
  box-shadow:
    0 19px 38px rgba(0, 0, 0, 0.3),
    0 15px 12px rgba(0, 0, 0, 0.22);
}

.grid-container {
  display: grid;
  grid-template-columns: 1fr 1fr 1fr;
  grid-template-rows: 1fr 1fr 1fr;
  grid-gap: 1em;
  margin-top: 1em;
}

.operand {
  background: rgb(255, 255, 255);
  border-radius: 10px;
  width: 50px;
  height: 50px;
  padding: 0.5em;
  font-size: 1.5em;
  font-weight: bold;
  color: #000;
  text-align: center;
  outline: none;
  margin: auto;
  border: none;
}

.operator {
  background: rgb(255, 255, 255);
  border-radius: 10px;
  width: 75px;
  height: 75px;
  padding: 0.5em;
  font-size: 1.5em;
  font-weight: bold;
  color: #000;
  text-align: center;
  outline: none;
  border: none;
  margin: auto;
  appearance: none;
}

.submit {
  grid-column: 1 / span 3;
  background-color: rgba(254, 204, 27, 1);
  height: 50px;
  font-size: 1.5em;
  margin: auto;
  color: #000;
  width: 100%;
  border-radius: 10px;
}

.result {
  grid-column: 1 / span 3;
  background-color: #fff;
  height: 50px;
  margin: auto;
  width: 100%;
  display: flex;
  justify-content: center;
  align-items: center;
  font-size: 1.5em;
  font-weight: bold;
  color: #000;
  border-radius: 10px;
}

.error-message {
  color: red;
  font-size: 1.2em;
  margin-top: 1em;
}
